The present invention relates to a side airbag apparatus that inflates and deploys an airbag in a space between a vehicle body side portion such as a side door and an occupant seated in a vehicle seat when an impact is applied from a side of the vehicle, thereby reducing the impact using the airbag to protect at least the lumbar region of the occupant.
A side airbag apparatus is effective as means for protecting an occupant seated in a vehicle seat when an impact is applied to the vehicle from a side due to a side collision. Such a side apparatus includes an inflator that discharges inflation gas in response to an impact to inflate and deploy an airbag in a space between an occupant and a vehicle body side portion. One type of such airbag apparatuses includes an airbag with a lumbar region protecting portion, which is inflated and deployed beside at least the lumbar region of an occupant to protect the lumbar region (see Japanese Laid-Open Patent Publication No. 2003-261000).
FIG. 18 shows the positional relationship of a body side portion 103, an airbag 105, and the pelvis 101 in the lumbar region 104 of an occupant. As shown in FIG. 18, the pelvis 101 includes a couple of ilia 102. An upper end portion 102U of each ilium 102 protrudes outward in the widthwise direction of the human body (left-right direction in FIG. 18). Thus, when the airbag 105 is inflated and deployed such that the lumbar region protecting portion 106 has an excessive thickness along the width of the vehicle in a space between the body side portion 103 and the upper end portion 102U of the ilium 102 on the vehicle outer side, the ilium 102 is pushed toward the inside of the vehicle through the upper end portion 102U. This generates an inward and downward rotation moment in the ilium 102 on the vehicle outer side as illustrated by arrow X in FIG. 18. As a result, an excessive load can be concentrated on a pubis 107 connected to the lower end of the ilium 102.